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SERPINC1 gene
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Gene

SERPINC1 Gene

The SERPINC1 gene provides instructions for making antithrombin, a critical protein that controls blood clotting by blocking the activity of clotting factors in the bloodstream.

Normal Function

The SERPINC1 gene (serpin family C member 1) provides instructions for making a protein called antithrombin (previously known as antithrombin III). Antithrombin is a type of serine protease inhibitor (serpin). Serpins help control several types of chemical reactions by blocking the activity of certain proteins. Antithrombin is found in the bloodstream and is essential for controlling blood clotting.

Antithrombin blocks the activity of proteins that promote blood clotting, especially a protein called thrombin. Antithrombin attaches (binds) to thrombin and certain other clotting proteins, which are then cleared from the bloodstream by the liver.

While one part of antithrombin binds to thrombin and other clotting proteins, another part of the protein binds to a substance called heparin. Antithrombin changes its shape when it binds to heparin. This change in shape allows antithrombin to inactivate clotting proteins at a much faster rate.

Health Conditions Related to Genetic Changes

Hereditary Antithrombin Deficiency

At least 220 mutations in the SERPINC1 gene have been found to cause hereditary antithrombin deficiency. Most of these mutations change single protein building blocks (amino acids) in antithrombin, which disrupts its ability to control blood clotting.

Hereditary antithrombin deficiency is divided into type I and type II based on the specific mutation in the SERPINC1 gene:

  • Type I: Caused by mutations that prevent the cell from producing antithrombin from the altered gene. Individuals with this type have only one working copy of the SERPINC1 gene in each cell, resulting in approximately half of the normal amount of antithrombin. Affected individuals do not have enough antithrombin to inactivate clotting proteins, which causes an increased risk for abnormal blood clots.
  • Type II: Caused by mutations that result in the production of an altered antithrombin with reduced activity. Individuals with this form typically have normal levels of antithrombin, but the protein does not function properly. Type II is further divided based on whether the mutation affects binding to:
    • Thrombin and other clotting factors (Type IIa)
    • Heparin (Type IIb)
    • Both (Type IIc)

Individuals with hereditary antithrombin deficiency type IIb have a lower risk of forming an abnormal blood clot than people with other forms of this condition because antithrombin is able to inactivate clotting proteins without heparin.

Other Names for This Gene

  • ANT3_HUMAN
  • antithrombin (aa 375-432)
  • antithrombin III
  • AT3
  • ATIII
  • coding sequence signal peptide antithrombin part 1
  • heparin cofactor I
  • MGC22579
  • serine (or cysteine) proteinase inhibitor, clade C (antithrombin), member 1
  • serine-cysteine proteinase inhibitor clade C member 1
  • serpin peptidase inhibitor, clade C (antithrombin), member 1
  • serpin peptidase inhibitor, clade C, member 1
  • signal peptide antithrombin part 1

Genomic Location

The SERPINC1 gene is found on chromosome 1.

Frequently Asked Questions

Individuals with hereditary antithrombin deficiency have a significantly increased risk of venous thromboembolism, which includes deep vein thrombosis (DVT) in the legs and pulmonary embolism (PE) in the lungs. Treatment for an active clot usually involves anticoagulant medications (blood thinners) such as heparin or warfarin. In some cases, especially for severe deficiencies or before surgery, antithrombin concentrate can be infused to raise levels temporarily. Long-term management depends on the severity of the deficiency and the patient's history of clots, with some patients requiring lifelong anticoagulation.
Pregnancy increases the risk of blood clots, and this risk is further elevated in individuals with antithrombin deficiency. Women with this condition are at higher risk for complications such as placental insufficiency, preterm birth, and preeclampsia. Management often involves prophylactic anticoagulation with low-molecular-weight heparin throughout pregnancy and for six weeks postpartum. Close monitoring by a high-risk obstetrician and a hematologist is essential to adjust medication doses and monitor for both clotting and bleeding risks.
Generally, individuals with hereditary antithrombin deficiency are not eligible to donate blood or plasma. Since the condition involves a functional or quantitative lack of a critical clotting regulator, donating plasma could potentially affect the recipient's coagulation profile, although the primary concern is the safety of the donor. More importantly, blood donation centers screen for conditions that might indicate underlying health issues. It is best to inform the medical staff of your specific genetic condition and consult with your hematologist before attempting to donate, as most guidelines recommend against it for individuals with known clotting disorders.
Diagnosis typically begins with a quantitative antithrombin activity test, which measures how well the protein is functioning in the blood. If this level is low, a functional assay is performed to confirm the deficiency. To distinguish between Type I (low quantity) and Type II (low quality) deficiency, an antigen level test is used. Type I shows low levels of both activity and antigen, while Type II shows normal antigen levels but low activity. Genetic testing for the SERPINC1 gene may also be performed to identify the specific mutation, which is useful for family screening and confirming the diagnosis.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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